The invention relates generally to digital video cameras, and more particularly to a digital video camera having a multi-focal lens system.
In conventional digital camera photography, typically a system of lenses is used to form an image which is captured by an image pickup device such as a charge-coupled device (CCD). The conventional lens system has, at any one time, a single focal length. By relative movement of lenses in the lens system, other focal lengths may be provided. With reference to FIG. 1, an image scene 10 may comprise a first object 12, such as a flower, positioned at a distance D1 close to a camera 20 having a lens or system of lenses 22. The lens system 22 may be configured to have a first focal length F1, such that objects very near the camera 20 falling within the first focal length F1 are in focus. The image scene 10 may farther comprise a second object 14, such as a rabbit, positioned at a distance D2 from the camera 20, falling outside the first focal length F1, and requiring a second focal length F2 to be in focus. Similarly, the image scene 10 may further comprise a third object 16, such as distant mountains, positioned at a great distance D3, falling outside both the first and second focal lengths F1 and F2, and requiring a third focal length F3 to be rendered in focus.
Multi-focal camera systems are known. U.S. Pat. No. 6,344,930 (Kancko et al.) discloses a total-focus imaging apparatus comprising a variable-focus lens unit having a focal position which is changeable at high speed. Known devices are limited, however, to providing composite images of fixed scenes, and are not suitable for the production of videos.
It would be desirable to provide an apparatus and associated method providing a video image having an extended depth of field wherein different objects at different distances are all in focus in a image of a common scene captured by a digital camera.